Manitoba Premier Brian Pallister responds to questions during a news conference at the first ministers meeting in Montreal on Friday, December 7, 2018. The Manitoba government has filed its own court challenge of the federal government's backstop carbon tax, following similar moves by Ontario and Saskatchewan.

Manitoba, Saskatchewan, Ontario and New Brunswick – all provinces lead by conservative governments – have refused federal Liberal demands to enact their own carbon levies. That prompted Ottawa to impose its own tax in those provinces, which started April 1 at $20 per tonne and will rise to $50 per tonne by 2022.

“The conduct by the federal government is unfair to Manitobans. It threatens jobs and economic growth throughout our province,” Manitoba Justice Minister Cliff Cullen said in a statement Wednesday.

Two years ago, the Manitoba government obtained a legal opinion from constitutional expert Bryan Schwartz. Schwartz said the federal government generally has the right to impose a carbon tax, but might be rebuffed if a province developed its own plan that would be equally effective in reducing emissions.

In the Saskatchewan court case, federal lawyers argued in February that Ottawa has the authority to enact a backstop carbon tax because climate change and greenhouse gas emissions are a matter of a national concern.